package bat.iog.hytool.tomcat;

import java.util.Collection;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.TimeUnit;

/**
 * As task queue specifically designed to run with a thread pool executor. The
 * task queue is optimised to properly utilize threads within a thread pool
 * executor. If you use a normal queue, the executor will spawn threads when
 * there are idle threads and you wont be able to force items onto the queue
 * itself.
 * 作为专门设计用于与线程池执行器一起运行的任务队列。 这
 * 任务队列经过优化以正确利用线程池中的线程
 * 执行人。 如果您使用普通队列，则执行程序将在以下时间产生线程
 * 有空闲线程，您将无法将项目强制进入队列
 * 本身。
 */
public class TaskQueue extends LinkedBlockingQueue<Runnable> {

    private static final long serialVersionUID = 1L;
    //protected static final StringManager sm = StringManager.getManager(TaskQueue.class);
    private static final int DEFAULT_FORCED_REMAINING_CAPACITY = -1;

    //private transient volatile ThreadPoolExecutor parent = null;

    // No need to be volatile. This is written and read in a single thread
    // (when stopping a context and firing the listeners)
    private int forcedRemainingCapacity = -1;

    public TaskQueue() {
        super();
    }

    public TaskQueue(int capacity) {
        super(capacity);
    }

    public TaskQueue(Collection<? extends Runnable> c) {
        super(c);
    }

//    public void setParent(ThreadPoolExecutor tp) {
//        parent = tp;
//    }


    /**
     * Used to add a task to the queue if the task has been rejected by the Executor.
     *
     * @param o         The task to add to the queue
     *
     * @return          {@code true} if the task was added to the queue,
     *                      otherwise {@code false}
     */
    public boolean force(Runnable o) {
//        if (parent == null || parent.isShutdown()) {
//            throw new RejectedExecutionException(sm.getString("taskQueue.notRunning"));
//        }
        return super.offer(o); //forces the item onto the queue, to be used if the task is rejected
    }


    /**
     * Used to add a task to the queue if the task has been rejected by the Executor.
     *
     * @param o         The task to add to the queue
     * @param timeout   The timeout to use when adding the task
     * @param unit      The units in which the timeout is expressed
     *
     * @return          {@code true} if the task was added to the queue,
     *                      otherwise {@code false}
     *
     * @throws InterruptedException If the call is interrupted before the
     *                              timeout expires
     *
     * @deprecated Unused. Will be removed in Tomcat 10.1.x.
     */
    @Deprecated
    public boolean force(Runnable o, long timeout, TimeUnit unit) throws InterruptedException {
//        if (parent == null || parent.isShutdown()) {
//            throw new RejectedExecutionException(sm.getString("taskQueue.notRunning"));
//        }
        return super.offer(o,timeout,unit); //forces the item onto the queue, to be used if the task is rejected
    }


    @Override
    public boolean offer(Runnable o) {
        //we can't do any checks
//        if (parent==null) {
//            return super.offer(o);
//        }
//        //we are maxed out on threads, simply queue the object
//        if (parent.getPoolSize() == parent.getMaximumPoolSize()) {
//            return super.offer(o);
//        }
//        //we have idle threads, just add it to the queue
//        if (parent.getSubmittedCount()<=(parent.getPoolSize())) {
//            return super.offer(o);
//        }
//        //if we have less threads than maximum force creation of a new thread
//        if (parent.getPoolSize()<parent.getMaximumPoolSize()) {
//            return false;
//        }
        //if we reached here, we need to add it to the queue
        return super.offer(o);
    }


    @Override
    public Runnable poll(long timeout, TimeUnit unit)
            throws InterruptedException {
        Runnable runnable = super.poll(timeout, unit);
//        if (runnable == null && parent != null) {
//            // the poll timed out, it gives an opportunity to stop the current
//            // thread if needed to avoid memory leaks.
//            parent.stopCurrentThreadIfNeeded();
//        }
        return runnable;
    }

    @Override
    public Runnable take() throws InterruptedException {
//        if (parent != null && parent.currentThreadShouldBeStopped()) {
//            return poll(parent.getKeepAliveTime(TimeUnit.MILLISECONDS),
//                    TimeUnit.MILLISECONDS);
//            // yes, this may return null (in case of timeout) which normally
//            // does not occur with take()
//            // but the ThreadPoolExecutor implementation allows this
//        }
        return super.take();
    }

    @Override
    public int remainingCapacity() {
        if (forcedRemainingCapacity > DEFAULT_FORCED_REMAINING_CAPACITY) {
            // ThreadPoolExecutor.setCorePoolSize checks that
            // remainingCapacity==0 to allow to interrupt idle threads
            // I don't see why, but this hack allows to conform to this
            // "requirement"
            return forcedRemainingCapacity;
        }
        return super.remainingCapacity();
    }

    public void setForcedRemainingCapacity(int forcedRemainingCapacity) {
        this.forcedRemainingCapacity = forcedRemainingCapacity;
    }

    void resetForcedRemainingCapacity() {
        this.forcedRemainingCapacity = DEFAULT_FORCED_REMAINING_CAPACITY;
    }

}

